1. Field of the Invention
The invention relates to the fabrication of 18% Ni maraging steel laminates of varying alloy compositions by roll bonding.
2. Description of the Prior Art
Maraging steels are iron-nickel martensites that are hardened by the precipitation of Mo and Ti containing intermetallic compounds. Cobalt, molybdenum, and titanium are added in various amounts to the basic alloy to produce a final product of varying strength levels from 200 to 350 KSI.
Methods of manufacturing cobalt-containing maraging steels of a specific alloy formulation are well known in the prior art. Recently, U.S. Pat. No. 4,443,254 describes a method for producing a cobalt-free version of the 250 and 300 KSI strength levels of the 18% Ni maraging steels.
It is known that steel can be roll bonded into laminate form. The steels to be bonded are heated to a selected temperature and then pressed together under high pressure to effect the bond. However, in quenched and tempered steels, there is a strong tendency for the laminates to separate and buckle during the quenching process due to non-uniform dimensional changes induced by rapid cooling and non-uniform expansion due to the formation of martensite.
The present invention addresses fabrication and lamination of a precipitation hardening type steel which can be air cooled from both the solution and aging temperature. Thus, the difficulties associated with the rapid cooling rate in the heat treatment of the quenched and tempered steel is avoided in the slow cooling of the maraging steels.